Implementing Image Zoom

1#include <SDL.h>
2#include <algorithm>
3#include <iostream>
4#include <string>
5
6class Image {
7public:
8  Image(std::string File,
9        SDL_PixelFormat* PreferredFormat =
10          nullptr)
11    : ImageSurface{SDL_LoadBMP(File.c_str())},
12      ZoomLevel{1.0f} {
13    // Constructor code remains the same
14  }
15
16  void Render(SDL_Surface* DestinationSurface,
17              int x, int y) {
18    int zoomedWidth = static_cast<int>(
19      ImageSurface->w * ZoomLevel);
20    int zoomedHeight = static_cast<int>(
21      ImageSurface->h * ZoomLevel);
22
23    SDL_Rect srcRect{
24      0, 0, ImageSurface->w, ImageSurface->h};
25    SDL_Rect destRect{
26      x, y, zoomedWidth, zoomedHeight};
27
28    SDL_BlitScaled(ImageSurface, &srcRect,
29                   DestinationSurface,
30                   &destRect);
31  }
32
33  void SetZoom(float zoom) {
34    // Prevent negative or zero zoom
35    ZoomLevel = std::max(0.1f, zoom);
36  }
37
38  float GetZoom() const { return ZoomLevel; }
39
40  // Rest of the class remains unchanged
41
42private:
43  SDL_Surface* ImageSurface;
44  float ZoomLevel;
45};
46
47int main() {
48  SDL_Init(SDL_INIT_VIDEO);
49  SDL_Window* window =
50    SDL_CreateWindow("Zoomable Image",
51                     SDL_WINDOWPOS_UNDEFINED,
52                     SDL_WINDOWPOS_UNDEFINED,
53                     800, 600, 0);
54  SDL_Surface* screenSurface =
55    SDL_GetWindowSurface(window);
56
57  Image img{
58    "example.bmp", screenSurface->format};
59
60  bool quit = false;
61  SDL_Event e;
62  while (!quit) {
63    while (SDL_PollEvent(&e) != 0) {
64      if (e.type == SDL_QUIT) {
65        quit = true;
66      } else if (e.type == SDL_KEYDOWN) {
67        switch (e.key.keysym.sym) {
68        case SDLK_PLUS:
69        case SDLK_KP_PLUS:
70          // Zoom in
71          img.SetZoom(img.GetZoom() * 1.1f);
72          break;
73        case SDLK_MINUS:
74        case SDLK_KP_MINUS:
75          // Zoom out
76          img.SetZoom(img.GetZoom() / 1.1f);
77          break;
78        }
79      }
80    }
81
82    SDL_FillRect(screenSurface, nullptr,
83      SDL_MapRGB(
84        screenSurface->format,
85        255, 255, 255
86      )
87    );
88    // Center of 800x600 window
89    img.Render(screenSurface, 400, 300);
90    SDL_UpdateWindowSurface(window);
91  }
92
93  SDL_DestroyWindow(window);
94  SDL_Quit();
95  return 0;
96}